Deal with crazy non-POSIX shells
Deal with crazy non-POSIX shells

Heroku's shell violates POSIX by having neither USER nor LOGNAME
environment variables exported. Catch this and provide a user-friendly
error message rather than a KeyError.

Fixes #33.

xarisd/honcho,myyk/honcho,janusnic/honcho,nickstenning/honcho,gratipay/honcho,nickstenning/honcho,gratipay/honcho